1. Technical Field
The present invention concerns a tape cartridge in which a flexible, elastic drive belt contacts the tape which is wound on tape spools and movement of the belt causes movement of the tape between the spools.
2. Background Information
Belt driven tape cartridges are frequently used to interface with computers where high tape speeds and rapid acceleration and deceleration of the tape are required. U.S. Pat. No. 3,692,255, incorporated herein by reference, discloses such a patent in which the magnetic recording tape is wound on two tape spools by an endless flexible belt in frictional contact with the magnetic tape on both spools. The endless flexible belt is wrapped around and driven by a capstan within the cartridge. The capstan itself is driven by a motor drive roller or drive puck which is external to the cartridge and is a portion of a recording/playback tape recorder mechanism into which the cartridge is inserted.
Tension in the tape is created by a difference in belt tension at each tape pack periphery caused by the controlled drag in the corner rollers. This tension difference causes the tape to wind from one spool to another as well as creating the desired value of tension at the read/write head. A minimum tape tension is necessary for reliable reading and recording of information. However, if the tape tension is too high undue wear occurs at the tape/head interface.
Because the belt has finite thickness, the centerline of the belt is moving at a slightly different speed than the tape pack peripheries. This causes the tape tension to increase as the tape winds from one tape hub to the other. If tape tension is profiled for running the tape cartridge in both the forward and reverse directions a bow-tie appears. This variation in tape tension results in a variation in the drive force required to propel the tape and a higher maximum drive force required at the end of the tape pack. A tape tension profile that is as flat as possible is desirable to limit the variation in drive force, reduce the maximum drive force required, and improve the performance of the cartridge over a variety of temperatures and after aging and use. The latter occurs because a flat tape tension profile allows for variation with temperature, age, and use without moving the cartridge out of the reasonable process window.
In addition to the overall variations in tape tension and drive force as the tape winds from one spool to another, small variations in tape tension may occur with a relatively high frequency during the process of running the tape cartridge. These small variations are called dynamic tape tension and result from small longitudinal movements of the tape caused by imperfections in the rotating components. High dynamic tape tension is undesirable because they may interfere with data reading or writing.
Conventional one layer belts that are more elastic show reduced bow-tie when compared to stiffer belts. Unfortunately, such elastic belts may also increase dynamic tape tension depending on the frequency of the rotating component imperfections.